Limit system for motor grader blade controls



June 10, 1969 Q AL ET AL 3,448,816

LIMIT SYSTEM FOR MOTOR GRADER BLADE CONTROLS Filed May 22, 1967 r r v I VENTORS I DUANE EBEAL5,D0/VAL0 R. ERCHTOLD n JAMES W. OER/EN, PAL/L L. ROSENBERGER AL FRED W. S/EV/A/G MERWYN 5.5mm .3% BY ATTORNEYS June 10, 1969 v D. E. BEALS ETAL 3,448,816

LIMIT SYSTEM FOR MOTOR GRADER BLADE CONTROLS Filed May 22, 1967 IgVENTORS DUANEEBtf/ILS, DONALD R. sec/4701.0 JAMES W OER/EN, PAUL C. POSENBERGER AL FRED WS/EV/NG, KERWV/VB'SM/TH ATTORNEYS June 10, 1969 BEALS ET AL 3,448,816

LIMIT SYSTEM FOR MOTOR GRADER BLADE CONTROLS- Filed May 22, 1967 Sheet 3 of 4 anua INVENTORS DUANE .EBEALS DONALD RBERCHTOLD JA MES W OBR/EN, PAL/L C POSENBERGER BYAL FRED W S/EV/NG KERWYNB. SM/TH z Z WP A T TORNEYS June 10, 1969 LIMIT s Filed May 22, 1967 D. E. BEALS ET AL 3,448,816

YSTEM FOR MOTOR GRADER BLADE CONTROLS Sheet Inf- O I M I I M DuA/vE E. BEA LS DONALD R BERCHTOLD JAMES W oBR/E/v, PAUL c. POSENBERGER AL FRED 14 5/5 V/N, KERWV/V B. SM/TH ATTORNEYS United States Patent 3,448,816 LIMIT SYSTEM FOR MOTOR GRADER BLADE CONTROLS Duane E. Beals, Donald R. Berchtold, James W. OBrien, Paul C. Rosenberger, Alfred W. Sieving, and Kerwyn B. Smith, Decatur, lll., assignors to Caterpillar Tractor Co., Peoria, 111., a corporation of California Filed May 22, 1967, Ser. No. 640,017

Int. Cl. E0213 3/84 US. Cl. 172-793 v Claims ABSTRACT OF THE DISCLOSURE A motor grader limiting mechanism for preventing damaging contact of a sideshifting rack, with a blade assembly suspended therebelow, during lifting and sideshifting blade motion according to a power control system. Elongated switc-hing means are disposed along substantially the entire rack undensurface to be actuatedby contact of the blade assembly at any point therealong and power control'system overriding meansare operably connected to the continuous switching means.

"Background of the invention i In a typical motor grader, a blade assembly including abl'ade, blade circle and drawbar means is suspended by two rotatable lift arms beneath an arcuate sideshifting rack assembly connected to a longitudinal frame of the motor grader. The lift arms rotate, in response to hydro-mechanical power controls about pivot points adjacent the motor grader frame to raise or lower the blade assembly. Simultaneous or separate sideshifting motion of the blade assembly is controlled through a connection between the blade circle and .the sideshifting rack by the hydraulically actuated power control system of the motor grader.

A problem arises when the motor grader blade approaches extreme operating positions, e.g., extreme bank cuts, maximum blade side reach, or even during nongra-ding travel of the motor grader with the blade lifted. During separate or simultaneous operation of the lifting and sideshifting controls to achieve these. blade positions, damaging contact is possible between the blade assembly and the sideshifting rack or between the lift arms at their extreme rotated posit-ions and the frame assembly. Such contact, if not controlled, may result in breaking or bending of the motor grader parts or may cause malfunctioning of the power control system controlling blade motion. The motor grader operator, usually concentrating on the blade position, may often be unaware of such imminent damaging contact and continue applying power to alter the blade assembly position. Thus, limit means are desirable to prevent or minimize the effect of such contacts between the motor grader parts.

One solution to the above problem has been to limit the amount of power which the power control system may exert for causing blade motion. For example, when blade motion is hydraulically controlled, pressure relief valves limit the hydraulic power exerted by the control system upon the blade assembly. However, these pressure relief valves only somewhat limit the force of contact 'between the motor grader parts. Further these pressure relief valves are sometimes unsatisfactory when motion of the blade is desired while the blade is operating against a grading load. Another solution has been to establish individual extreme operating limits for the lift controls and sideshifting controls of the blade assembly. However, with simultaneous lift and sideshift control limits for the blade assembly, the over-all blade motion limits must be excessively curtailed to prevent damaging contact between the motor grader parts.

3,448,816 Patented June 10, 1969 Summary of the invention The present invention .provides 'a limit mechanism which does not unnecessarily curtail overall blade motion, but which prevents damaging contact particularly between the blade assembly and the sideshifting rack assembly. Elongated switching means are disposed along substantially the entire sideshifting rack undersurfaces to be actuated by contact of the blade assembly at any point there-long. The switching means are operably connected with an override means suitable to interrupt power system motion control over the blade assembly.

Brief, description of the drawings FIG. 1 is a partial isometric view of a motor grader showing the connection of a blade assembly thereto;

FIG. 2 is a sectioned view in elevation of a motor grader of FIG. 1 showing the blade assembly positioned for extreme bank cutting;

FIG. 3 is a schematic representation of the possible points of damaging contact between the motor grader parts along with switches and circuitry for preventing such damaging contact;

FIG. 4 is an end view in section, of the preferred switching means; and

FIG. 5 is a schematic representation of an alternate embodiment of the limit system.

Description of the preferred embodiments Having reference to FIGS. 1 and 2, a typical motor grader 11 has a major longitudinal frame 12 from which a blade assembly 13 is suspended therebenea-th by means of a pair of rotating lift arms 14 and 16. To raise or lower the blade assembly, the lift arms 14 and 16 are rotated independently or simultaneously about their respective pivot points, indicated at 17 and 18 in FIG. 2, located generally adjacent the sides of the frame. For sideshifting control of the blade assembly, an arcuate sideshifting rack .19 is disposed beneath the frame so that the blade assembly is suspended below the rack. The blade assembly comprises a grading blade 21 which is connected to a rotatable blade ring 22 and a structural member 23 which is disposed across the blade ring and connected to the lift arms. The blade assembly is connected to the sideshifting rack by an arm 20 for controlling sideshifting blade motion. The motor grader operator controls sideshifting and lifting motion of the blade assembly through the sideshifting rack and the lift arms by means of a power control system 24 which is described in detail infra with reference to FIG. 3.

It is to be noted, particularly with reference to FIG. 2, that simultaneous or separate sideshifting and lifting operation of the blade assembly may tend to cause damaging contact by the blade assembly at any point along an undersurface 25 of the sideshifting rack 19. Further the lift arms, being individually rotatable to raise or lower the blade assembly, may come into damaging contact with the frame at one or more of the points indicated at 26.

To limit lifting and sideshifting operation of the blade assembly by the power control system and prevent the above-noted damaging contact, elongated switches 27 are disposed along effectively the entire undersurface 25 of the sideshifting rack and are capable of being actuated by contact at any point therealong. To insure that the blade ring actuates the switch means 27 at extreme blade positions, a pair of actuating pads shown at 28 is disposed on a portion of the blade ring, as shown, which will usually come in contact with the rack to exert more positive actuating pressure upon the rack switch means 27. As further assurance of switch actuation, the elongated rack switches 27 are spaced apart from the rack undersurfaces 25 by switch spacer pads 30 disposed therebetween. In FIG. 2, one of the pads 28 is shown in actuating contact with the elongated switch. A contact-actuated switch 29 is also disposed upon the frame at each of the points 26 where the rotating lift arms may tend to make damaging contact with the frame. The rack switch 2 7 is actuatable by contact of the blade assembly at any point thereon, and each of the lift arm switches 29 is actuatable by contact of one of the rotatable lift arms thereon.

Referring to FIG. 3, the rack and lift arm switches are electrically connected in parallel with an override relay switch 31 which is operably connected with the power control system 24 such that on actuation of any of the rack and lift arm switches, the override switch 31 causes interruption of the control system power toprevent further lifting or sideshifting motion in the blade assembly. The electrical connection between the parallel switches 27 and 29 and the grounded power control system 24 is provided by a common ground 32 to the motor grader frame for the parallel switches and a common electrical lead 33. Retractable electrical lead 34 connects the rack switches 27 with the common lead 33 on the motor grader frame to prevent interruption of the circuit by operation of the rack. The power control system preferably includes spring-loaded brake means indicated at 36 in FIG. 1, which is electricallyassociated with the limit system, for example by servo units (not shown), to be engaged and thus lock the blade assembly in place simultaneously with operation of the override switch 31 according to actuation of any of the parallel switches 27 and 29. Thus, free blade assembly motion is prevented, the grading load on the blade assembly is held and the motor grader operator may easily regain blade assembly control as discussed below. The power control system 24 also preferably includes an alarm means 37, such as a warning light (see FIG. 3) which is operated by actuation of any of the switches 27 and 29 to notify the motor grader operator of overriding of the power control system. Further the power control system 24 includes switch means 38 which is operable by the grader operator to inactive the limit mechanism and regain control over the blade assembly through the power control system 24.

The power control system 24 is preferably a hydromechanical system having a pair of solenoid valves 39 therein and override means which, upon electrical activation, energize the solenoid valves and cause them to dump hydraulic fluid pressure in the power control system 24 and thus override its lifting and sideshifting operation of the blade assembly. Actuation of any of the parallel switches 27 and 29 closes the normally open override switch 31 by causing current flow in a coil 41 associated with the override switch to place battery 42 in activating electrical connection with the solenoid valves to achieve the above-noted overriding effect and operate the spring loaded brakes of the power control system to lock the blade assembly in place. Once the motor grader operator is aware of van override condition, he operates the switch 38 which is connected with the override switch and solenoid valve circuit in a manner to cause the override switch 31 to then open and thus regains control of the blade assembly through the power control system.

Having reference now also to FIG. 4, each rack switch 27 is a contact-actuated switch having an inner and an outer elongated flexible electrical conductor 43 and 44, respectively. The inner conductor 43 is disposed adjacent the rack undersurface 25. The outer elongated conductor 44 is disposed in parallel, spaced-apart relation from the inner conductor such that contact of the blade assembly at any point therealong will cause electrical actuating contact to be made between the conductors 43 and 44. Each lift arm switch 29 is of similar construction and is disposed at one of the frame points 26 to be acmated by rotating contact of one of the lift arms thereupon. Within each of the rack and lift arm switches 27 and 29, one of the conductors 43 and 44 is connected with 4 the common ground 32 while the other is connected to the control system by common lead 33 so that closing of the override switch 31 may be effected by contact between the conductors of any of the parallel switches 27 or 29.

Even with the above-described limiting mechanism, damaging contact could still occur between the time that the lift assembly or lift arms contacts and actuates one of the parallel switches and the time when sideshifting or lifting motion of the blade assembly through the power control system is finally limited. To prevent such damage by overtravel of either the blade assembly or lift arms, the switches 27 and 29 are preferably encased along their lengths with a resilient means 46, for example rubber, of suitable flexibility and thickness that, on contact of the blade assembly or lift arms with one or more of the switches 27 and 29, the resilient means 46 will be resiliently compressed at least partly following actuating contact of the switch conductors 43 and 44. Such an electrical switch is commercially available from Tapeswitch Corporation of America under the tradenames Tapeswitch and Controflex.

Thus the present limit mechanism is economical and is of durable and reliable construction. The switching and electrical circuitry of the present limiting mechanism is very responsive to prevent damaging contact between the motor grader parts. It may be seen that the parallel switches 27 land 29, disposed in the dirt-laden environment of the blade assembly, are sealed in by the resilient means 46 and thereby are not susceptible to fouling. Further, the exposed electrical components of the limiting mechanism which may be subject to damage can be readily inspected and repaired.

An alternate embodiment of the present invention is illustrated in FIG. 5 wherein similar limit means are provided to override the power control system when one or both of the lift arms approaches an axial limit of its motion and wherein control of the blade assembly is automatically returned to the grader operator at the termination of lift arm interference.

Contact-actuated switches 51, 52, 53 and 54 are disposed upon the grader frame at the points where damaging contact may be made by the lift arms (illustrated in FIGS. 2 and 3) and are preferably of similar construction as switches 29. Switches 51 and 52 are at the upper and lower axial limits of the lefthand lift arm while switches 53 and 54 are respectively at the upper and lower axial limits of the righthand lift arm. The lift arm switches 51-54 have one of their conductors 44 electrically connected in parallel with a control system 56 which is similar to system 24 of FIG. 3 and comprises an override switch 31', alarm means 37', two solenoid dump valves 39' and a DC source 42'. As with the control system of FIG. 3, current flow in switch 31' causes it to close and energize the solenoid valves, which then dump hydraulic fluid pressure in the power control system to override the lifting and sideshifting operation of the blade assembly.

' However, it is to be noted that the power control system does not contain a reset switch similar to switch 38 in FIG. 3 for returning control to the grader operator. Rather, pressure switches 57, 58, 59 and 61 are provided to automatically return control over the blade assembly to the grader operator when interference in the lift arms has been eliminated. One of the pressure switches is connected to the other conductor 43' in each of the lift arm switches by means'of an electrical connector 62. Each of the pressure switches also has a ground connection to provide a complete circuit along with the control system, particularly the ground connections of the solenoid valves. The pressure switches are of a type which receive hydraulic fluid and which are normally open and nonconducting until they are closed by a preselected minimum pressure exerted therein by the hydraulic fluid. The pressure switches are also in fluid communication with the hydraulic portion of the control system by means of fluid conduits which are not shownfor purposes of simplicity. For example, pressure switch 57, which is associated with lift arm switch 52. at the lower axial limit of the lefthand lift arm, is in fluid communication with a port in the control system whereat hydraulic fluid acts to lower the lefthand lift arm. Similarly, pressure switch 58 is associated with the upper lefthand lift arm switch and is in communication with the control system to receive hydraulic fluid which acts to raise the left lift arm. Pressure switch 59 is associated with the upper righthand lift arm switch 53 and is in fluid communication with the control system to receive hydraulic fluid which acts to raise the righthand lift arm. Pressure switch 61 is associated with the lower righthand lift arm switch 54 and is in communication withthe control system to receive hydraulic fluid which acts to lower the righthand lift arm. V

.To describe the operation of the pressure switches in conjunction with'the lift arm switches, assume that the righthand lift arm is raised untilit is approaching into possibly damaging contact with the motor grader frame. Before, such. damaging contact is made, the lift arm actuates or closes the upper, righthand lift arm switch 53 which would normally send an override signal to the control system.;-However, before such an override signalmay betransmitted, pressure switch 59 mustalso be closed to provide a complete electrical circuit. Closure of the pressure switch 59' results when hydraulic fluid acting to raise the righthand lift arm. rises to a predetermined pressure. Thus, as the right lift arm is raised andcomes into contact with the lift arm switch, the lift arm switch 53 is also closed resulting in the safety circuit being energized. An override signal occurs in the control system to close override switch 31', energize the solenoid valve 39' and dump hydraulic fluid pressure in the power control system which results in an override of the lifting .and sideshifting operation of the blade assembly. At this point it is to be noted that when the. power control system is overridden, pressure of the hydraulic fluid which was acting to raise the righthand lift arm will fall with a resulting fluid pressure drop in pressure switch 59. Upon the resulting reopening of pressure switch 59, the override signal to the power control system is terminated whereupon override switch 31' is reopened, the solenoid valves are de-energized and hydraulic fluid pressure again builds up in the control system. If, upon this reoccurrence of hydraulic pressure in the control system, the lift arm is still in contact with upper lift armswitch 53, lift arm switch 53 and the pressure switch 59 will both again be closed as described above with a resulting cyclical operation of the override switch 31' between its open and closed position until the interference of the lift arm with the upper lift arm switch and the frame is eliminated. Each time the override switch is actuated, current will also flow in the alarm light 37' causing it to flash on and off and give the motor grader operator a visual warning of the interference condition in the lift arm. Once the lift arm is moved out of contact with the upper lift arm switch 53 and the motor grader frame, the combination of the lift arm switch and the pressure switch will not interfere with the operation of the blade assembly. The above operation described with reference to the upper righthand lift arm switch 53 and the associated pressure switch 59 will similarly occur in the other pairs of lift arm switches and pressure switches upon interference at the other radial limits of the lift arms.

Thus, the above alternate embodiment provides a limiting system for the lift arms which will prevent damaging contact between the lift arms and the motor grader frame. Control of the blade assembly is automatically returned to the motor grader operator whenever the interference conditions of the lift arms have been eliminated without requiring operation of a reset switch as in the first-described embodiment.

What is claimed is:' Y

1. Blade motion limiting apparatus in a motor grader having a blade assembly suspended beneath a sideshifting rack and a power control system for moving said blade assembly in both lifting and sideshifting modes where damaging contact may occur between the blade assembly and the sideshifting rack, the apparatus comprismg:

contact actuated switching means disposed along substantially the entire sideshifting rack surfaces susceptible of damaging contact by the blade assembly to be actuated by contact of the blade assembly at any point therealong; and override means operatively associated with said switching means and the power control system, said override means responsive to actuation of said switching means to terminate control of the power control system over motion of the blade assembly. 2. Blade motion limiting apparatus according to claim 1 wherein the blade assembly lifting motion is controlled through rotatable lift arms disposed adjacent a longitudinal frame of the motor grader, the lift arms tending to contact the frame at extreme rotational positions of the lift arms, the apparatus further comprising:

switching means disposed uponthe frame at each extreme rotational contacting point of the lift arms thereon, each to be proximity actuated by one of the lift arms, said lift arm switching means operatively associated with said override means; and locking means disposed with relation to the blade assembly to lock the blade assembly from further motion at any position thereof, said locking means and said override means simultaneously operated by actuation of at least one of said rack switching means and said lift arm switching means. 3. Blade motion limiting apparatus according to claim 2 wherein:

said rack switching means is at least one elongated switch comprising first and second spaced apart electrical conductors, said first conductor disposed adjacent the sideshifting rack undersurface, said second conductor disposed parallel thereto to be driven into switch actuating electrical contact with said first electrical conductor by contact of the blade assembly at any point therealong; and

said lift arm switching means comprises a plurality of contact-actuated electrical switches.

4. Blade motion limiting apparatus according to claim 3, to prevent damage by overtravel of the blade assembly and lift arms after actuating contact thereof upon at least one of said rack switching means and said lift arm switching means and prior to operation of said override means and said locking means, wherein resilient means are disposed with relation to each of said rack switching means and said lift arm switching means to be resiliently compressed at least partially subsequent to actuation of each said rack and lift arm switching means.

5. In a motor grader having a longitudinal frame, the combination comprising:

a blade assembly;

rotating lift arms acting about pivot points adjacent the frame and connected to said blade assembly to suspend said blade assembly below said frame and to raise and lower said blade assembly, said lift arms tending to contact said frame at their extreme rotational positions;

an arcuate sideshifting rack assembly connected to the frame such that an undersurface of the rack is contactable by said blade assembly;

at least one elongated, arcuate, contact-actuated switch encased in resilient means and disposed along the length of said rack undersurface to be actuatable by contact of said blade assembly at any point therealong;

multiple contact-actuated switch means encased in resilient material and disposed on said frame at the points where said lift arms tend to make contact therewith, each lift arm switch actuatable by contact of one of the lift arms thereon, said lift arm switches and said arcuate rack switches being electrically connected in parallel; and

a hydraulic power control system for controlling lifting and sideshifting operation of said blade assembly, said power control system including electrically-activated solenoid valves for releasing operating hydraulic pressure in said system and spring-loaded brake means activatable to lock the blade assembly in position, said solenoid valves and said brake means electrically connected with said parallelly connected switches to be activated by actuation of at least one of said parallel switches, said control system including alarm means operatively associated with said parallel switches to be activated by actuation of at least one of said parallel switches, said control means including reset means for reestablishing operating hydraulic pressure in said control system and releasing said brake means.

6. Blade motion limiting apparatus in a motor grader having a blade assembly suspended below a frame element by means of a pair of rotatable lift arms adjacent the frame element and a power control system for raising and lowering the blade assembly through the lift arms, the combination comprising:

proximity actuated switching means disposed upon the frame element at each extreme rotational limit of the lift arms;

override means operatively associated with said switching means and the power control system, said override means responsive to actuation of said switching means to interrupt the power control systems control over motion of the blade assembly through the lift arms;

alarm means operatively associated with said switching means to be activated by actuation of said switching means; and

reset means operatively associated with said control system and operable to reestablish motion control of the control system over the blade assembly.

7. The blade motion limiting apparatus of claim 6 further defined by:

said switching means being a plurality of switches elec' trically connected in parallel;

brake means operatively associated with said switch means and the blade assembly, said brake means responsive to actuation of one of said parallel switches to prevent further motion of the blade assembly, said reset means being operatively associated with said brake means and operable to release said brake means.

8. Blade motion limiting apparatus in a motor grader having a blade assembly suspended below a frame element by means of a pair of rotatable lift arms adjacent the frame element and a power control system for raising and lowering the blade assembly through the lift arms, the combination comprising:

a contact-actuatable switch disposed upon the frame element at each extreme rotational contacting point of the lift arms thereon;

override means operatively associated with said switches and the power control system, said override means responsive to actuation of any of said switches to terminate control of the power control system over the blade assembly through the lift arms; and

automatic reset means operatively associated with said override means and the power control system, said reset means reestablishing motion control of the power control system over the blade assembly when rotational power transmitted by the power'control system to the lift arms is reduced to a suitable level.

9. The blade motion limiting apparatus of claim 8 further defined by alarm means associated with said override means and operable simultaneously with said override means to provide an alarm signal when an override condition exists.

10. The blade motion limiting apparatus of claim 8 where the power control system is at least partially hydraulic and wherein:

any one of said lift arm switches causes an override signal to be received by said override means upon being contacted by one of the lift arms;

said override means is operable by the override signal to activate at least one servovalve in the control system which dumps hydraulic fluid therein and which restores operating hydraulic fluid pressure when the override signal is terminated; and

said automatic reset means comprises a pressure switch operatively associated with each lift arm switch and the power control system, said pressure switch operable to terminate the override signal upon sensing reduced fluid pressure in the power control system resulting from the dumping of fluid by the servovalve.

References Cited UNITED STATES PATENTS 2,258,890 10/ 1941 Gustafson 172-793 ANTONIO F. GUIDA, Primary Examiner.

ALAN E. KOPECKI, Assistant Examiner. 

